The present invention relates to control panels used with security systems, and in particular, to a control panel which disconnects conventional telephones from the publicly switched telephone network while allowing a high frequency AC signal to continue to be connected to the domestic telephone service.
Home security alarm control panels in most application share the use of the telephone service with the conventional telephone, however, the control panel has the capability seizing the telephone service and disconnecting the other devices on the service. In this way, the control panel can seize the telephone line to report alarm events to a security monitoring station even if the telephone line was in use.
This approach has worked well for many years and for most applications there is little inconvenience caused by the control panel seizing the telephone line upon demand. Often the household telephone devices are not in use when the security system seizes the line. For example, the security is most often armed when no one is present and therefore, if the control panel seizes the line, no inconvenience occurs as the line was not in use. Some security systems are used to monitor perimeter sensors, such as doors and windows while the occupants of the household are present. For example, the system may be armed at night. Once again, the use of the telephone has not been seriously impaired.
More recently, telephone communication companies have provided households with the capability to simultaneously receive and transmit the conventional low frequency DC signal used for telephone service, and a high frequency AC signal used for computer communications. A DSL modem can be connected to the telephone line at any point in the household and receive data over the telephone service while additionally allowing simultaneous use of the telephone in the normal manner. In some circumstances, the high frequency AC signal does provide a small noise component heard on the conventional telephone and a blocking filter can be provided for each telephone device.
Unfortunately, this dual usage of a single line telephone service in combination with a control panel sharing the service can cause problems. For example, if the user has decided to download a large file from a web server or other remote computer over the telephone service, if the control plane seizes the line, it will disconnect all devices in the household including the computer and as such, interrupt and corrupt the downloading of the data. To overcome this problem, the DSL modem could be connected to the telephone service upstream of the control panel, however, this is not always practical and it creates serious installation problems at additional cost.
The present invention provides a solution to overcome the above problems.
A high frequency bypass circuit for a telephone line according to the present invention, comprises Tip and Ring inputs, Tip and Ring security control panel outputs, and Tip and Ring high frequency outputs for a local telephone service. The circuit includes a DC branch connected to the Tip and Ring inputs which branch conducts low frequency telephone signals to the Tip and Ring security panel outputs. The circuit has an AC coupled high frequency branch connecting the Tip and Ring inputs to the Tip and Ring high frequency outputs.
With this arrangement, the AC coupled high frequency branch transmits DSL signals and other high frequency signals and blocks the transmission of low frequency audio telephone signals through the high frequency branch. The control panel which is connected immediately downstream of the bypass circuit, continues to control the low frequency DC telephone signals to the household telephone system. The control panel can seize this low frequency transmission path and disconnect the remaining service from the low frequency signal. In this way, the conventional phones on the household service are disconnected and the control panel functions in its normal manner.
The high frequency AC signal provided to the bypass circuit bypasses the control panel and continues to provide the high frequency component to the household service. In this way, if data is being transmitted over the telephone lines to or from a computer connected on the household telephone system, this transmission of data will continue and not be interrupted by the state of the control panel.
In a preferred aspect of the invention, the DC branch of the bypass circuit includes a filter which blocks the transmission of high frequency signals. Preferrably, this filter blocks transmission of any signal having a frequency above five KHz.
According to yet a further aspect of the invention, the high frequency branch includes capacitors for blocking the low frequency telephone signals.
According to yet a further aspect of the invention, a high frequency pass filter is used to block the low frequency audio telephone signals on the high frequency branch of the circuit.
A security control panel according to the present invention, has the high frequency bypass circuit included in the circuitry of the control panel. The control panel includes ring and tip inputs for connection to a telephone line for receiving DC low frequency telephone audio signals and AC high frequency telephone signals, a signal dividing circuit for conducting the DC low frequency telephone audio signals through a DC branch of the circuit and conducting the AC high frequency telephone signals through an AC branch of the circuit from the Tip and Ring inputs to the Tip and Ring outputs of the control panel used to connect with a household telephone system.
The control panel further includes a communication module and line seize switch arrangement. The line seize switch arrangement is controlled by the communication module. The line seize switch arrangement in one position connects the Tip and Ring inputs with the Tip and Ring outputs and in a second position, disconnects the Tip and Ring inputs from the Tip and Ring outputs. With this arrangement, the AC high frequency telephone signals are conducted by the AC branch between the Tip and Ring inputs and outputs and the DC low frequency telephone signals are selectively conducted between said Tip and Ring inputs and outputs depending upon the line seize switch arrangement.